Google recruiters have allegedly been told not to hire staff from companies such as search rival Yahoo and biotechnology specialist Genentech.

A former Google human resources employee, who left the company last year, told the story to Silicon Valley's Mercury News.

The worker claimed that Google maintained a list of companies that should not be on the CVs of potential employees as their current place of employment if they wanted to be hired.

The news could be of interest to the US Department of Justice (DoJ), which is currently investigating the hiring practices of Google, Yahoo and Apple to determine whether the firms deliberately avoided headhunting each others' key staff.

The DoJ said that a formal pact not to hire senior staff from each other would hamper the ability of staff to sell their services to the highest bidder, and therefore stifle competition.

Google declined to comment on the Mercury News report, but said it was co-operating with the DoJ investigation.